The present invention relates to methods for preparing large amounts of immunogenic material that is useful as a vaccine for the prevention and/or treatment of cancer. The vaccine is comprised of noncovalent complexes of heat shock proteins (hsp), including, but not limited to, hsp70, hsp90, gp96, and protein disulfide isomerase, and antigenic peptides. The vaccine is capable of eliciting or augmenting a subject""s immune response against a particular cancer.
Cancer is characterized primarily by an increase in the number of abnormal cells derived from a given normal tissue. The disease process also involves invasion of adjacent tissues by these abnormal cells, and spread of these abnormal cells to regional lymph nodes and to distant sites (metastasis) via the circulatory system. Clinical data and molecular biologic studies indicate that cancer is a multistep process that begins with minor preneoplastic changes, which may under certain conditions progress to neoplasia.
Pre-malignant abnormal cell growth is exemplified by hyperplasia, metaplasia, or most particularly, dysplasia (for review of such abnormal growth conditions, see Robbins and Angell, 1976, Basic Pathology, 2d Ed., W. B. Saunders Co., Philadelphia, pp. 68-79.) Hyperplasia is a form of controlled cell proliferation involving an increase in cell number in a tissue or organ, without significant alteration in structure or function. As but one example, endometrial hyperplasia often precedes endometrial cancer. Metaplasia is a form of controlled cell growth in which one type of adult or fully differentiated cell substitutes for another type of adult cell. Metaplasia can occur in epithelial or connective tissue cells. Atypical metaplasia involves a somewhat disorderly metaplastic epithelium. Dysplasia is frequently a forerunner of cancer, and is found mainly in the epithelia; it is the most disorderly form of non-neoplastic cell growth, involving a loss in individual cell uniformity and in the architectural orientation of cells. Dysplastic cells often have abnormally large, deeply stained nuclei, and exhibit pleomorphism. Dysplasia characteristically occurs where there exists chronic irritation or inflammation, and is often found in the cervix, respiratory passages, oral cavity, and gall bladder.
The neoplastic lesion may evolve clonally and develop an increasing capacity for invasion, growth, metastasis, and heterogeneity, especially under conditions in which the neoplastic cells escape the host""s immune surveillance (Roitt, I., Brostoff, J. and Male, D., 1993, Immunology, 3rd ed., Mosby, St. Louis, pps. 17.1-17.12).
Vaccination has eradicated certain diseases such as polio, tetanus, chicken pox, measles, etc. in many countries of the world. This approach has exploited the ability of the immune system to prevent infectious diseases. Such vaccination with non-live materials such as proteins generally leads to an antibody response or CD4+ helper T cell response (Raychaudhuri and Morrow, 1993, Immunology Today, 14:344-348). On the other hand, vaccination or infection with live materials such as live cells or infectious viruses generally leads to a CD8+ cytotoxic T-lymphocyte (CTL) response. A CTL response is crucial for protection against cancers, infectious viruses and bacteria. This poses a practical problem, for, the only way to achieve a CTL response is to use live agents which are themselves pathogenic. The problem is generally circumvented by using attenuated viral and bacterial strains, or by killing whole cells which can be used for vaccination. These strategies have worked well but the use of attenuated strains always carries the risk that the attenuated agent may recombine genetically with host DNA and turn into a virulent strain. Thus, there is need for methods which can lead to CD8+ CTL response by vaccination with non-live materials such as proteins in a specific manner.
The era of tumor immunology began with experiments by Prehn and Main, who showed that antigens on the methylcholanthrene (MCA)-induced sarcomas were tumor specific in that transplantation assays could not detect these antigens in normal tissue of the mice (Prehn et al., 1957, J. Natl. Cancer Inst. 18:769-778). This notion was confirmed by further experiments demonstrating that tumor specific resistance against MCA-induced tumors can be elicited in the mouse in which the tumor originated (Klein et al., 1960, Cancer Res. 20:1561-1572).
In subsequent studies, tumor specific antigens were also found on tumors induced with other chemical or physical carcinogens or on spontaneous tumors (Kripke, 1974, J. Natl. Cancer Inst. 53:1333-1336; Vaage, 1968, Cancer Res. 28:2477-2483; Carswell et al., 1970, J. Natl. Cancer Inst. 44:1281-1288). Since these studies used protective immunity against the growth of transplanted tumors as the criterion for tumor specific antigens, these antigens are also commonly referred to as xe2x80x9ctumor specific transplantation antigensxe2x80x9d or xe2x80x9ctumor specific rejection antigens.xe2x80x9d Several factors can greatly influence the immunogenicity of the tumor, including, for example, the specific type of carcinogen involved, immunocompetence of the host and latency period (Old et al., 1962, Ann. N.Y. Acad. Sci. 101:80-106; Bartlett, 1972, J. Natl. Cancer Inst. 49:493-504).
Most, if not all, carcinogens are mutagens which may cause mutation, leading to the expression of tumor specific antigens (Ames, 1979, Science 204:587-593; Weisburger et al., 1981, Science 214:401-407). Some carcinogens are immunosuppressive (Malmgren et al., 1952, Proc. Soc. Exp. Biol. Med. 79:484-488). Experimental evidence suggests that there is a constant inverse correlation between immunogenicity of a tumor and latency period (time between exposure to carcinogen and tumor appearance) (Old et al., 1962, Ann. N.Y. Acad. Sci. 101:80-106; and Bartlett, 1972, J. Natl. Cancer Inst. 49:493-504). Other studies have revealed the existence of tumor specific antigens that do not lead to rejection, but, nevertheless, can potentially stimulate specific immune responses (Roitt, I., Brostoff, J. and Male, D., 1993, Immunology, 3rd ed., Mosby, St. Louis, pp. 17.1-17.12).
Heat shock proteins (hsps) are also referred to interchangeably as stress proteins. The first stress proteins to be identified were proteins synthesized by a cell in response to heat shock. To date, three major families of hsp have been identified based on molecular weight. The families have been called hsp60, hsp70 and hsp90 where the numbers reflect the approximate molecular weight of the stress proteins in kilodaltons. Many members of these families were found subsequently to be induced in response to other stressful stimuli including nutrient deprivation, metabolic disruption, oxygen radicals, and infection with intracellular pathogens. (See Welch, May 1993, Scientific American 56-64; Young, 1990, Annu. Rev. Immunol. 8:401-420; Craig, 1993, Science 260:1902-1903; Gething et al., 1992, Nature 355:33-45; and Lindquist et al., 1988, Annu. Rev. Genetics 22:631-677).
The major hsps can accumulate to very high levels in stressed cells, but they occur at low to moderate levels in cells that have not been stressed. For example, the highly inducible mammalian hsp70 is hardly detectable at normal temperatures but becomes one of the most actively synthesized proteins in the cell upon heat shock (Welch et al., 1985, J. Cell. Biol. 101:1198-1211). In contrast, hsp90 and hsp60 proteins are abundant at normal temperatures in most, but not all, mammalian cells and are further induced by heat (Lai et al., 1984, Mol. Cell. Biol. 4:2802-2810; van Bergen en Henegouwen et al., 1987, Genes Dev. 1:525-531).
Studies on the cellular response to heat shock and other physiological stresses revealed that the hsps are involved not only in cellular protection against these adverse conditions, but also in essential biochemical and immunological processes in unstressed cells. The hsps accomplish different kinds of chaperoning functions. For example, hsp70, located in the cell cytoplasm, nucleus, mitochondria, or endoplasmic reticulum, (Lindquist, S. et al., 1988, Ann. Rev. Genetics 22:631-677) are involved in the presentation of antigens to the cells of the immune system, and are also involved in the transfer, folding and assembly of proteins in normal cells. Hsps are capable of binding proteins or peptides, and releasing the bound proteins or peptides in the presence of adenosine triphosphate (ATP) or low pH.
Other stress proteins involved in folding and assembly of proteins include, for example, protein disulfide isomerase (PDI), which catalyses disulfide bond formation, isomerization, or reduction in the endoplasmic reticulum (Gething et al., 1992, Nature 355:33-45).
Heat shock proteins are among the most highly conserved proteins in existence. For example, DnaK, the hsp70 from E. coli has about 50% amino acid sequence identity with hsp70 proteins from excoriates (Bardwell et al., 1984, Proc. Natl. Acad. Sci. 81:848-852). The hsp60 and hsp90 families also show similarly high levels of intra families conservation (Hickey et al., 1989, Mol. Cell. Biol. 9:2615-2626; Jindal, 1989, Mol. Cell. Biol. 9:2279-2283). In addition, it has been discovered that the hsp60, hsp70 and hsp90 families are composed of proteins that are related to the stress proteins in sequence, for example, having greater than 35% amino acid identity, but whose expression levels are not altered by stress.
Srivastava et al. demonstrated immune response to methylcholanthrene-induced sarcomas of inbred mice (1988, Immunol. Today 9:78-83). In these studies, it was found that the molecules responsible for the individually distinct immunogenicity of these tumors were identified as cell-surface glycoproteins of 96kDa (gp96) and intracellular proteins of 84 to 86kDa (Srivastava, P. K. et al., 1986, Proc. Natl. Acad. Sci. USA 83:3407-3411; Ullrich, S. J. et al., 1986, Proc. Natl. Acad. Sci. USA 83:3121-3125). Immunization of mice with gp96 or p84/86 isolated from a particular tumor rendered the mice immune to that particular tumor, but not to antigenically distinct tumors. Isolation and characterization of genes encoding gp96 and p84/86 revealed significant homology between them, and showed that gp96 and p84/86 were, respectively, the endoplasmic reticular and cytosolic counterparts of the same heat shock proteins (Srivastava, P. K. et al., 1988, Immunogenetics 28:205-207; Srivastava, P. K. et al., 1991, Curr. Top. Microbiol. Immunol. 167:109-123). Further, hsp70 was shown to elicit immunity to the tumor from which it was isolated but not to antigenically distinct tumors. However, hsp70 depleted of peptides was found to lose its immunogenic activity (Udono, M., and Srivastava, P. K., 1993, J. Exp. Med. 178:1391-1396). These observations suggested that the heat shock proteins are not immunogenic per se, but form noncovalent complexes with antigenic peptides, and the complexes can elicit specific immunity to the antigenic peptides (Srivastava, P. K., 1993, Adv. Cancer Res. 62:153-177; Udono, H. et al., 1994, J. Immunol., 152:5398-5403; Suto, R. et al., 1995, Science, 269:1585-1588).
The use of noncovalent complexes of stress protein and peptide, purified from cancer cells, for the treatment and prevention of cancer has been described in PCT publications WO 96/10411, dated Apr. 11, 1996, and WO 97/10001, dated Mar. 20, 1997 (see also copending U.S. patent applications Ser. No. 08/796,319 filed Feb. 7, 1997 by Srivastava and Chandawarkar and Ser. No. 08/796,316 filed Feb. 7, 1997 by Srivastava, each of which is incorporated by reference herein in its entirety). Stress protein-peptide complexes can also be isolated from pathogen-infected cells and used for the treatment and prevention of infection caused by the pathogen, such as viruses, and other intracellular pathogens, including bacteria, protozoa, fungi and parasites. See PCT publication WO 95/24923, dated Sep. 21, 1995. Immunogenic stress protein-peptide complexes can also be prepared by in vitro complexing of stress protein and antigenic peptides, and the uses of such complexes for the treatment and prevention of cancer and infectious diseases has been described in PCT publication WO 97/10000, dated Mar. 20, 1997. The use of stress protein-peptide complexes for sensitizing antigen presenting cells in vitro for use in adoptive immunotherapy is described in PCT publication WO 97/10002, dated Mar. 20, 1997.
The purification of stress protein-peptide complexes has been described previously; see for example, PCT Publication WO 95/24923, dated Sep. 21, 1995. For the purpose of preparing a vaccine against cancer, the amount of immunogenic material obtainable for use is directly related to the amount of starting cancer cells. Since only a small number of cancer cells can be obtained from a subject, especially if the cancer is at an early stage, the supply of cancer cells for producing the hsp-peptide complex is often very limited. Although some type of cancer cells can be cultured in vitro, such is less preferable than using complexes known to be representative of the cancer cells in vivo. For commercial production of a vaccine or therapeutic agent, a constant supply of large amounts of hsp-peptide complexes is advantageous. Thus, there is a need for a dependable long-term source of hsp-peptide complexes that does not depend on availability of fresh cell samples from cancer patients. The methods of the present invention do not depend on a large or continuous supply of such cancer cells from a subject, and can be used to provide hsp-peptide complexes even when only a very small amounts of tumor tissue is available from a patient for use.
The present invention relates to methods for producing increased amounts of immunogenic material which can be used for prevention and treatment of cancer. The immunogenic compositions prepared by the methods of the invention comprise noncovalently associated molecular complexes of a heat shock protein (hsp) and an antigenic (or immunogenic) peptide. The complexes prepared by the methods of the invention are intracellularly produced complexes comprising hsps from a selected recombinant host cell and antigenic peptides expressed from cDNAs of a cancer cell; the antigenic peptides of the complex are thus representative of antigenic peptides found in such cancer cell. The present invention provides methods for making a cDNA library from cancer cells, using the cDNA library to produce by recombinant DNA methods in host cells immunogenic hsp-peptide complexes that confer immunity to the cancer cells in an individual to which the complexes are administered.
Generally, the methods of the invention comprise obtaining (e.g., isolating) cancer cells from one or more individuals, preparing RNA from the cancer cells, making cDNA from the RNA, introducing the cDNA into host cells, culturing the host cells so that the cancer-derived cDNAs are expressed, and purifying heat shock protein-peptide complexes from the host cells.
The cDNA prepared from cancer cell RNA, herein referred to as xe2x80x9ccancer cDNAxe2x80x9d, is optionally amplified prior to introduction into a host cell for expression. The cDNAs are optionally inserted into a cloning vector for replication purposes prior to expression. The cDNAs are inserted into an expression vector or intrachromosomally integrated, operatively linked to regulatory element(s) such as a promoter, for purposes of expressing the encoded proteins in suitable host cells in vitro. The cDNAs are introduced into host cells where they are expressed by the host cells, thereby producing intracellularly noncovalent complexes of hsps and peptides (including those peptides encoded by the cancer cDNAs). The recombinant host cells can be cultured on a large scale for production of large amounts of the immunogenic complexes. The cancer cDNA library can be stored for future use (e.g., by lyophilization or freezing), or expanded by replication in a cloning vector in suitable host cells to meet increased demand for the immunogenic complexes.
The immunogenic compositions prepared from the host cells expressing the cancer cDNAs comprise complexes of hsps of the host cell noncovalently associated with peptides, inter alia, those derived from the cancer cells from which the RNA was originally derived. Such complexes can induce an immune response in a patient against the cancer cells that is therapeutically or prophylactically efficacious. Preferably, the patient is the subject from whom the cancer cells used to make cDNA were obtained. Alternatively, the cancer cells can be from one or more subjects different from the patient but having cancer of the same tissue type (e.g., stomach cancer, breast cancer, colon cancer, lung cancer, etc.)
Optionally, host cells for expression of the cancer cDNAs can also be genetically engineered to coexpress recombinantly one or more hsp genes so that increased amounts of complexes comprising immunogenic peptides noncovalently associated with the hsps can be produced. Particular compositions of the invention and their methods of preparation are described in the sections and subsections which follow.